Don't exaggerate or build up the importance of something; don't make a big deal out of something. The phrase is often used to complain that someone is exaggerating a problem or alleged wrongdoing. So I ate your leftovers. Geez, don't make a federal case out of it! A: "I know you borrowed my new sweater without asking me first." B: "Oh, come on, don't make a federal case out of it."